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conclusive information。 The German armament manufacturers
endeavoured to solve the problem by using smoking shells or
missiles fitted with what are known as tracers。 By following the
ascensional path of the projectiles as revealed by the smoke it
was possible to draw certain conclusions。 But these were by no
means convincing or illuminating； as so many factors affected the
issue。
Despite the peculiar and complex difficulties associated with the
problem it was attacked some what boldly。 In this trying field
of artillery research the prominent German armament
manufacturers； Krupp of Essen and Ehrhardt of Dusseldorf； played
a leading part； the result being that before the airship or the
aeroplane was received within the military fold； the
anti…aircraft gun had been brought into the field of applied
science。 The sudden levelling…up serves to illustrate the
enterprise of the Germans in this respect as well as their
perspicacity in connection with the military value of aircraft。
Any gun we can hope to employ against aircraft with some degree
of success must fulfil special conditions； for it has to deal
with a difficult and elusive foe。 Both the lighter…than…air and
the heavier than…air craft possess distinctive features and
varying degrees of mobility。 Taking the first…named； the
facility with which it can vary its altitude is a disconcerting
factor； and is perplexing to the most skilful gunner； inasmuch as
he is called upon to judge and change the range suddenly。
On the other hand； the artilleryman is favoured in certain
directions。 The range of utility of the airship is severely
limited。 If its avowed mission is reconnaissance and conclusive
information concerning the disposition of forces； artillery and
so forth is required； experience has proved that such work cannot
be carried out satisfactorily or with any degree of accuracy at a
height exceeding 5；000 feet； and a distance beyond six miles。
But even under these circumstances the climatic conditions must
be extremely favourable。 If the elements are unpropitious the
airship must venture nearer to its objective。 These data were
not difficult to collect； inasmuch as they were more or less
available from the results of military observations with captive
balloons； the conditions being somewhat similar。 With the
ordinary captive balloon it has been found that； in clear
weather； a radius of about 3 3/4 miles at the maximum elevation
constitutes its range of reliable utility。
With the aeroplane； however； the conditions are very dissimilar。
In the first place the machine owing to its diminutive size as
compared with the airship； offers a small and inconspicuous
target。 Then there is its high independent speed； which is far
beyond that of the airship。 Furthermore its mobility is greater。
It can wheel； turn sharply to the right or to the left； and
pursue an irregular undulating flight in the horizontal plane；
which renders it well nigh impossible for a gunner to pick it up。
The machine moves at a higher relative speed than that at which
the gun can be trained。 It is the rapid and devious variation
which so baffles the gunner； who unless he be highly skilled and
patient； is apt to commence to fire wildly after striving for a
few moments； and in vain； to pick up the range； he trusts to luck
or depends upon blind…shooting； which invariably results in a
waste of ammunition。
A gun； to be of tangible destructive efficiency when directed
against aircraft； especially those depending upon the gas…bag for
equilibrium； must be of special design。 It must be capable of
firing at an angle only a few degrees less than the absolute
vertical； and in order to follow the rapid and involved movements
of its objective； must be so mobile that it can be trained
through a complete circle at any angle of inclination less than
its maximum。 At the same time； if the weapon is being used in
field operations it must be mounted upon a carriage of adequate
mobility to enable it to follow the airship； and thereby keep
pace with the latter； so that the aerial craft may be sorely
harassed if not actually hit。 The automobile is the obvious
vehicle for this duty； and it has accordingly been extensively
used in this service。
The automobile and the gun mounted thereon follow widely
different lines。 Some vehicles are designed especially for this
duty； while others are improvisations； and be it noted； in
passing； that many of the latter have proved more serviceable
than the former。 Still； the first…named is to be preferred；
inasmuch as necessarily it is designed to meet the all…round
requirements imposed； and consequently is better able to stand up
to the intended work； whereas the extemporised vehicle is only
serviceable under favourable conditions。
The Krupp Company has evolved many designs of anti…aircraft
motor…driven guns〃Archibalds〃 the British airmen term them with
emphatic levity。 They are sturdily…built vehicles fitted with
heavy motors； developing from 40 to 50 horse…power； with the
chassis not widely dissimilar from that adopted for motor…omnibus
traffic。 Consequently； they are not necessarily condemned to the
high…roads； but within certain limits are able to travel across
country； i。e。； upon fields or other level expanses； where the
soil is not unduly soft。
But the very character of the problem rendered the evolution of
the vehicle a somewhat perplexing matter。 There were many
factors which had to be taken into consideration； and it was
possible to meet the imposed requirements only within certain
limits。 In the first place； the weight of the gun itself had to
be kept down。 It was obviously useless to overload the chassis。
Again； the weight of the projectile and its velocity had to be
borne in mind。 A high velocity was imperative。 Accordingly； an
initial velocity varying from 2；200 to 2；700 feet per second；
according to the calibre of the gun； was determined。
Moreover； as mobility was an indispensable condition； the gun had
to be so mounted that it could be fired from the motor…car even
if the latter were travelling at high speed。 This requirement
entailed another difficulty。 The gun had to be mounted in such a
manner as to enable the gunner to train it easily and readily
through the complete circle and through its complete range of
vertical inclination。 As the result of prolonged experiments it
was ascertained that the most suitable arrangement was a pedestal
mounting； either within a turret or upon an open deck。 To meet
the weight of the gun； as well as the strains and stresses
incidental to firing； the chassis was strengthened； especially
over the rear axle near which the mounting is placed。
The heaviest gun of this type is the 10。5 centimetre （4 1/4…inch）
quick…firer； throwing a shell weighing nearly forty pounds； with
an initial velocity of 2；333 feet per second。 This 〃Archibald〃
is totally unprotected。